forked from OpenZeppelin/openzeppelin-contracts
/
Initializable.sol
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/
Initializable.sol
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// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (proxy/utils/Initializable.sol)
pragma solidity ^0.8.0;
import "../../utils/Address.sol";
/**
* @dev This is a base contract to aid in writing upgradeable contracts, or any kind of contract that will be deployed
* behind a proxy. Since proxied contracts do not make use of a constructor, it's common to move constructor logic to an
* external initializer function, usually called `initialize`. It then becomes necessary to protect this initializer
* function so it can only be called once. The {initializer} modifier provided by this contract will have this effect.
*
* TIP: To avoid leaving the proxy in an uninitialized state, the initializer function should be called as early as
* possible by providing the encoded function call as the `_data` argument to {ERC1967Proxy-constructor}.
*
* CAUTION: When used with inheritance, manual care must be taken to not invoke a parent initializer twice, or to ensure
* that all initializers are idempotent. This is not verified automatically as constructors are by Solidity.
*
* [CAUTION]
* ====
* Avoid leaving a contract uninitialized.
*
* An uninitialized contract can be taken over by an attacker. This applies to both a proxy and its implementation
* contract, which may impact the proxy. To initialize the implementation contract, you can either invoke the
* initializer manually, or you can include a constructor to automatically mark it as initialized when it is deployed:
*
* [.hljs-theme-light.nopadding]
* ```
* /// @custom:oz-upgrades-unsafe-allow constructor
* constructor() initializer {}
* ```
* ====
*/
abstract contract Initializable {
/**
* @dev Indicates that the contract has been initialized.
* @custom:oz-retyped-from bool
*/
uint8 private _initialized;
/**
* @dev Indicates that the contract is in the process of being initialized.
*/
bool private _initializing;
/**
* @dev Modifier to protect an initializer function from being invoked twice.
*/
modifier initializer() {
bool isTopLevelCall = _setInitializeStep(1);
_;
if (isTopLevelCall) {
_initializing = false;
}
}
/**
* @dev Modifier to allow the execution of `onlyInitializing`-protected methods, after the original initialization
* step, through "reinitializer". These "reinitializer" are essential to configure modules that are added through
* upgrades and that require an initialization step.
*/
modifier reinitializer(uint8 version) {
bool isTopLevelCall = _setInitializeStep(version);
_;
if (isTopLevelCall) {
_initializing = false;
}
}
/**
* @dev Modifier to protect an initialization function so that it can only be invoked by functions with the
* {initializer} modifier, directly or indirectly.
*/
modifier onlyInitializing() {
require(_initializing, "Initializable: contract is not initializing");
_;
}
function _setInitializeStep(uint8 version) private returns (bool) {
// If the contract is initializing we ignore whether _initialized is set in order to support multiple
// inheritance patterns, but we only do this in the context of a constructor, and for the lowest level
// of initializers, because in other contexts the contract may have been reentered.
if (_initializing) {
require(version == 1 && !Address.isContract(address(this)), "Initializable: contract is already initialized");
return false;
} else {
require(_initialized < version, "Initializable: contract is already initialized");
_initializing = true;
_initialized = version;
return true;
}
}
}